1. Field of the Invention
This invention relates to a light modulation element for modulating light from a light guide plate by means of a flexible thin film displaced by the electromechanical operation, an exposure unit for exposing a sensitive material to light with the light modulation element, and a flat-panel display unit for displaying an image with the light modulation element.
2. Description of the Related Art
For example, a liquid crystal display, a plasma display, and the like are named as representative thin flat-panel display units. However, in the liquid crystal display, light from backlight is allowed to pass through a large number of layers of a polarizing plate, a transparent electrode, and a color filter and a problem of lowering the light use efficiency arises; in the plasma display, diaphragm formation for discharge is executed for each pixel, thus it is difficult to provide high intensity at high efficiency as definition becomes high, and drive voltage is also high, leading to an increase in costs.
To solve such problems, in recent years, a flat-panel display unit for displacing a flexible thin film by the electromechanical operation, thereby modulating light from a light source for displaying an image has been developed. For example, such a flat-panel display unit is described in the following document:
Waveguide Panel Display Using Electromechanical Spatial Modulators, 1988, SID International Symposium Digest of Technical Papers, p.1022-p.1025.
The flat-panel display unit comprises a plurality of parallel optical waveguides 92 placed side by side on a front glass 91 and an LED (light emitting diode) array 95 connected to one end side of the optical waveguides 92 via a light guide member 94 having a microlens 93, as shown in FIG. 16. The LED array 95 comprises a plurality of light emission parts listed in one dimension and the light emission parts are provided in a one-to-one correspondence with the optical waveguides 92. A plurality of parallel flexible thin films (light switches) 96 are placed side by side above the optical waveguides 92 with a gap in a direction orthogonal to the optical waveguides 92. A rear glass 97 with only a part brought into contact with the flexible thin film 96 is placed above the flexible thin films 96 and supports the flexible thin films 96 displaceably.
In the described flat-panel display unit 90, when a voltage is applied to an electrode on a predetermined flexible thin film 96, the flexible thin film 96 is displaced by an electrostatic force in a direction in which it approaches the optical waveguide 92 side, as shown in FIG. 17. On the other hand, the LED array 95 emits light based on an image signal in synchronization therewith. Then, light advancing while being totally reflected in the optical waveguide 92 is guided into the flexible thin film 96, is reflected on a mirror 98 placed in the flexible thin film 96, and again is made incident on the optical waveguide 92 in a direction roughly perpendicular to the optical waveguide 92. The light made incident on the optical waveguide 92 in the direction roughly perpendicular to the optical waveguide 92 cannot hold the angle of total reflection, passes through the optical waveguide 92, and is emitted from the front glass 91 side.
According to the flat-panel display unit, the flexible thin film 96 is displaced by an electrostatic force, thus the operation of the flexible thin film 96 can be followed at high speed; in addition, unlike the liquid crystal display, light is not allowed to pass through a large number of layers and unlike the plasma display, diaphragm formation in a discharge section and a high-voltage drive circuit become unnecessary, so that it is made possible to provide a fast and inexpensive flat-panel display unit.
However, in the described flat-panel display unit 90 of the optical waveguide type, light is emitted by means of the reflection film in the flexible thin film, thus the emitted light involves a directivity and viewability worsens.
For color display, an LED array of a number of colors needs to be used as a light source and the light source and the optical system are limited; in addition, the unit configuration becomes intricate and the manufacturing process becomes complicated, resulting in an increase in costs.
It is therefore an object of the invention to provide a light modulation element less depending on a viewing angle, enabling highly efficient luminescent display, and providing high light use efficiency although the structure is simple, an exposure unit using the light modulation element, and a flat-panel display unit using the light modulation element.
According to this invention, there is provided a light modulation element comprising a light guide body for guiding light from a light source and a flexible thin film having a fluorescent material being provided facing the light guide body, characterized in that the distance between the flexible thin film and the light guide body is changed by the electromechanical operation and light emission of the fluorescent material excited by the guided light is controlled.
In the light modulation element, the flexible thin film having the fluorescent material is displaced by the electromechanical operation, whereby light guided from the light source into the light guide body is guided into the flexible thin film side for exciting the fluorescent material to emit light or light is not guided, whereby light modulation is executed. Since the flexible thin film thus comprises the fluorescent material, the structure and the manufacturing process of the element are simplified and the manufacturing costs can be reduced drastically. Since the fluorescent material is used, a scattered light emission state is entered at the light emission time and dependency of a viewing angle is scarcely produced, improving viewability. Further, light is applied directly to the fluorescent material, thus the fluorescent material can be excited for emitting light in high efficiency.
Various electromechanical effects of an electrostatic effect, an electromagnetic effect, a piezoelectric effect, etc., can be used as means of the electromechanical operation.
In this invention, the electromechanical operation is performed by generating an electrostatic force between the flexible thin film and the light guide body.
In the light modulation element, a voltage is applied to the flexible thin film and the light guide body, whereby an electrostatic force is generated between the flexible thin film and the light guide body, the flexible thin film performs the electromechanical operation smoothly at high speed and reliably by the generated electrostatic force, and stable light modulation is executed. The element using an electrostatic force can be provided by executing a simple manufacturing process for forming an electrode on the flexible thin film, and the costs can be reduced. Further, because of voltage drive type, it is made possible to execute low-voltage drive by optimizing the material and shape of the thin film.
In this invention, the light guide body is formed with a first electrode, the flexible thin film is formed with a second electrode, and a voltage is applied to the first electrode and the second electrode, thereby generating an electrostatic force.
In the light modulation element, a voltage is applied to the first electrode on the light guide body side and the second electrode on the flexible thin film side, whereby an electrostatic force is generated between the electrodes and the second electrode on the flexible thin film side is displaced, whereby light modulation is executed. Thus, a necessary structure can be formed on a single substrate and it is made possible to manufacture the element with high accuracy at low costs.
In this invention, the fluorescent material is a fluorescent layer formed on a surface of the flexible thin film.
In the light modulation element, the fluorescent film can be formed on the surface of the flexible thin film by a general thick film formation method, such as print, a spray method, or application, a vacuum film formation method, etc., so that the fluorescent materials can be provided easily and uniformly, and unevenness in light emission can be well prevented.
In this invention, the flexible thin film is made of a resin material and the fluorescent material made of a fluorescent pigment of fine particles is mixed in the flexible thin film.
In the light modulation element, the fluorescent material made of a fluorescent pigment of fine particles is mixed in the flexible thin film, whereby the flexible thin film and the fluorescent material can be formed at the same time, and resin has good workability, thus thin film formation is facilitated and it is made possible to use various flexible thin film materials and fluorescent materials.
In this invention, the flexible thin film is made of a resin material and the fluorescent material made of an organic fluorescent dye is melted into the flexible thin film.
In the light modulation element, the fluorescent material made of an organic fluorescent dye of fine particles is melted into the flexible thin film, whereby the fluorescent material can be distributed in the flexible thin film extremely uniformly in a simple process, and unevenness in light emission can be better prevented. Luminescent color proper to the organic fluorescent dye can be provided.
In this invention, the flexible thin film is formed with a reflection film for reflecting light emitted by the fluorescent material toward the light guide body.
In the light modulation element, the light emitted by the fluorescent material can be reflected in the light emission direction of the light modulation element without wasting the light directed in the direction opposite to the light emission direction of the element, and the light use efficiency can be enhanced.
In this invention, the reflection film is used as a second electrode.
In the light modulation element, the reflection film is also made to function as a second electrode, so that the element configuration is simplified, the manufacturing process can be simplified, and the costs can be reduced.
In this invention, a filter layer for allowing light from the light source to pass through and reflecting light emitted by the fluorescent material is placed between the fluorescent material of the flexible thin film and the light guide body.
In the light modulation element, a filter layer is placed between the light guide body and the fluorescent material provided on the flexible thin film, whereby when light is guided into the flexible thin film, light from the light source passes through the filter layer; on the other hand, light emitted by the fluorescent material is reflected on the filter layer, so that the light directed in the direction opposite to the light emission direction of the light modulation element can be reflected in the light emission direction. Thus, the light use efficiency of the light from the fluorescent material can be enhanced.
In this invention, light from the light source is guided from a side of the light guide body.
In the light modulation element, light from the light source is guided from the side of the light guide body and can be emitted from the surface of the light guide body. Therefore, the light source placement space in the thickness direction of the light modulation element is not unnecessary and the element can be thinned as much as possible
In this invention, light from the light source is guided from a surface of the light guide body on an opposite side to the flexible thin film.
In the fight modulation element, it is made possible to guide the light from the light source from either the face or the back of the light guide body, the light guide area of the light guide body for receiving the light from the light source is increased, and light modulation for emitting light in high intensity can be executed easily.
In this invention, the light guide body is an optical waveguide.
In the light modulation element, the optical waveguide is formed as the light guide body, whereby the light guided into the optical waveguide can be modulated.
In this invention, the light modulation element comprises a plurality of parallel optical waveguides formed on a substrate, a plurality of light sources that can be controlled separately with at least one of the optical waveguides made to correspond to one pixel, and a plurality of flexible thin films orthogonal to the optical waveguides, wherein the quantity of flight from the light source is changed and light emission of the fluorescent material excited is controlled by the electromechanical operation of the flexible thin film.
In the light modulation element, the light quantity of each of the light sources provided in a one-to-one correspondence with the parallel optical waveguides is changed and light emission of the fluorescent material excited is controlled by the electromechanical operation of the flexible thin film, whereby it is made possible to control the light modulation elements separately, and it is also made possible to perform multiple gradation control by adjusting the light quantity.
In this invention, the light source is a light emission array element.
In the light modulation element, for example, light emission array elements of laser deflection and laser diode array, an inorganic LED array, an organic LED array, inorganic EL (electroluminescence), a fluorescent display tube, FED (field emission display), CRT (cathode-ray tube), etc., can be used, and high intensity can be easily provided by using a plurality of light emission elements in combination. To use a plurality of light modulation elements, the light modulation elements can be easily controlled separately.
In this invention, the light source is made up of a light emission body and a light modulation array element.
In the light modulation element, for example, a fluorescent lamp, a discharge lamp, etc., can be used as the light emission body and a liquid crystal array, an optical crystal array, etc., can be used as the light modulation array. High-intensity light emission body is modulated by means of the light modulation array, whereby the light modulation elements can be driven separately for executing light modulation in high intensity.
In this invention, the light guide body is a light guide plate.
In the light modulation element, the light guide plate is formed as the light guide body, whereby the light guided into the light guide plate can be modulated.
The light modulation element in this invention is arranged like a one-dimensional or two-dimensional matrix wherein the first electrodes and the second electrodes are placed like stripes orthogonal to each other, each of the light modulation elements is formed at each of the intersection points of the first electrodes and the second electrodes, and simple matrix drive is executed.
In the light modulation element, the first electrodes are arranged in parallel, the second electrodes are arranged in parallel, orthogonal to the first electrodes, and the light modulation elements are formed at the intersection points of the first and second electrodes, thereby arranging the light modulation elements like a matrix. This configuration enables simple matrix drive to be executed for the light modulation elements.
The light modulation elements in this invention are arranged like a one-dimensional or two-dimensional matrix wherein either the first electrode or the second electrode is used as a pixel electrode, a switch mechanism for supplying an image signal to the pixel electrode is provided for each of the light modulation elements, and active matrix drive is executed.
In the light modulation elements, either the first electrode or the second electrode is used as a pixel electrode and a switch mechanism for supplying an image signal to the pixel electrode is provided for each of the light modulation elements, thereby arranging the light modulation elements like a one-dimensional or two-dimensional matrix, and active matrix drive can be executed. Thus, the light modulation elements can be driven easily and contrast can be more enhanced.
In the light modulation element in this invention, the guided light is ultraviolet light.
In the light modulation element, ultraviolet light for exciting the fluorescent material can be guided for executing light modulation. Since ultraviolet light excites the fluorescent material to emit light, visible light and infrared light can be easily provided and exposure and display at various wavelengths are enabled. Generally, a large number of types of fluorescent materials excited by ultraviolet ray to emit visible light exist and thus practical use is easily made.
In the light modulation element in this invention, a shield part is provided in an area other than the light emission part of the fluorescent material.
In the light modulation element, a shield part is provided in an area other than the light emission part of the fluorescent material, whereby to display an image, the contrast of the image can be more enhanced.
In the light modulation element in this invention, the guided light is single-color light and wherein the fluorescent material comprises a plurality of different luminescent colors.
In the light modulation element, the fluorescent materials of a plurality of different luminescent colors are caused to emit light, whereby any desired color can be displayed and color display can be produced easily.
In the exposure unit in this invention, the light modulation element is driven based on image information, whereby a record medium can be exposed to modulated light from the light modulation element.
In the flat-panel display unit of this invention, the light modulation element is driven based on image information, whereby an image can be displayed based on modulated light from the light modulation element.